Air blast circuit breaker with parallel resistances



March 19, 1957 H. FORWALD 2,785,117

AIR BLAST CIRCUIT BREAKER WITH PARALLEL RESISTANCES Filed Feb. 15, 1955Fig. Q /0 r1 L; I... LJ .0 I; ,7 9 /4 INVENTOR. Haakorz Tom/cud Zfltomey.

AIR BLAST CIRCUIT BREAKER WITH PARALLEL RESISTANCES Haakon Forwald,Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget,Vasteras, Sweden, a Swedish corporation Application February 15, 1955,Serial No. 488,212

Claims priority, application Sweden February 17 1954 Claims. (Cl.200-148) The present invention relates to electric air blast circuitbreakers, in which the main breaking contacts are arranged in acompressed air container, always filled with air under pressure, inwhich container a resistance is coupled in parallel with the mainbreaking gap over a certain auxiliary breaking gap, also arranged in thecontainer. The invention has for its purpose to produce, in a simpleway, a flow of compressed air against the auxiliary breaking gap andthus facilitating the extinction of the are appearing there. Theinvention is chiefly characterized thereby that the auxiliary breakinggap is arranged immediately before the outlet of a separate compartmentin the container, so that, when at the opening of the circuit breakerair escapes from the container across the main breaking gap, thelowering of the pressure in the container also causes a flow of air fromthe separate compartment across the contacts of the auxiliary breakinggap. The arrangement may either be such that the escape of air from saidseparate compartment commences immediately after the said lowering ofthe pressure in the container, but it can also be such that the escapeof air from the separate compartment commences first when the auxiliarybreaking contacts are separated, e. g. by so designing the movablecontact in the auxiliary breaking gap that, when this is closed, themovable contact closes the outlet opening from said separatecompartment, which opening is then opened, when the movable contactmoves to its open position.

A form of the invention is schematically shown on the accompanyingdrawing, Fig. 1, which schematically shows a circuit breaker with a mainbreaking gap and an auxiliary breaking gap, Whereas Fig. 2 shows amodified form. On the drawing, 1 designates a base, on which two pillarinsulators 2 and 3, carrying a compressed air container 4, are fastened.In the wall of the container a mechanism housing 5 is inserted, whichcontains an operating member for the movable contact 6 of the mainbreaking gap and an outlet valve 7 from the air container. Thestationary contact 8 of the main breaking gap is attached to aleading-through insulator, which consists of an insulating cylinder 9closed at the top by a cover 10 of metal. 11 designates also a mechanismhousing inserted in the wall of the compressed air container, whichhousing contains the operating menr her for the movable contact 12 ofthe auxiliary breaking gap, the stationary contact of said gap beingdesignated by 13. This contact is arranged at the lower end of a metalcylinder 14, which, at the lower end, is acc0mmodated to the stationarycontact 13 in such a way that a slot 15 is formed between the stationarycontact and the cylinder. The cylinder 14 is attached to the cover 16,which, at the top, closes the cylinder 17 serving as nited States PatentO 'ice a leading-through insulator. 18 designates a resistance, which isconnected to the two covers 10 and 16. The mechanism housings 5 and 11are over a pipe line 19 in communication with a container for compressedair for the operation of the operating devices in said mechanismhousings. Compressed air is delivered to the container 4 through adelivery line not shown on the drawing, which is suitably arrangedinside one of the insulators 2 or 3.

This device acts in the following way. In opening the circuit breaker,compressed air is delivered to the mechanism housing 5 through the pipeline 19, which air, on one hand, acts on the movable contact 6, so thatit is separated from the contact 8, and, on the other hand, opens theescape valve 7. When air escapes through this valve, the pressure in thecontainer 4 falls, and consequently the air in the cylinder 14 willescape from the cylinder 14 through the slot 15 and is brought incontact with the are formed between the contacts 12 and 13, so that thisare is extinguished.

In the form shown in Fig. 1 the escape of air from the cylinder 14commences immediately after that the pressure in the container 4 islowered. in the arrangement shown in Fig. 2, however, the cylinder 14 isreplaced by a container 20 arranged inside the container 4, the formercontainer being provided with an outlet opening 21, in which the movablecontact 12 of the auxiliary breaking gap fits. When compressed air isdelivered to the mechanism housing 11, the movable contact 12 is moveddownwards and leaves the contact 13 simultaneously as the opening 21 isliberated, so that the air in the container 2% can escape through saidopening and come in contact with the are between the contacts 12 and 13.In the Wall of the container 29 a valve 22 is arranged, through whichthe space inside the container 20 is again filled with compressed air,when the pressure in the container 4 is subsequently increased.

1 claim as my invention:

1. An air blast circuit breaker having a compressed air container andcomprising main fixed and movable breaking contacts and auxiliary fixedand movable breaking contacts arranged in said container, means forminga separate compressed air compartment, an opening arranged in closeproximity to the auxiliary breaker gap and providing communicationbetween the said container and the said separate compartment, and aircontrol means whereby the lowering of the air pressure in the containerdue to the opening of the circuit breaker and the consequent escape ofair from the container permits air to escape from the said separatecompartment through said Opening and into contact with the arc gapformed between the contacts of the said auxiliary breaking gap.

2. An arrangement according to claim 1, in which the movable contact ofthe auxiliary breaking contacts closes the said opening when theauxiliary contacts are in their closed position.

3. An air blast circuit breaker having a compressed air container andcomprising main breaking contacts located in the container, means forpermitting the escape of air from the container to extinguish the are atthe main gap, means forming a separate compressed air compartment, anopening providing communication between the interior of said compartmentand the interior of said container, a fixed and a movable contactforming auxiliary breaking contacts within said container, the saidopening being arranged to divert the air from said compartment to saidauxiliary gap when the air pressure in the container is reduced by theescape of air there- References Cited in the file of this patent UNITEDSTATES PATENTS 2,153,400 Trencham Apr. 4, 1939 2,453,555 Thommen Nov. 9,1948 2,665,351 Forwald Jan. 5, 1954 FOREIGN PATENTS 469,892 GreatBritain Aug. 3, 1937

